Fiber-reinforced composite articles made from fibers having coupling-initiator compounds and methods of making the articles

ABSTRACT

Methods of making a fiber-reinforced composite article are described. The methods may include providing fibers to an article template, where the fibers have been treated with a coupling-initiator compound. They may further include providing a pre-polymerized mixture that includes a monomer and a catalyst to the article template. The combination of the fibers and the pre-polymerized mixture may be heated to a polymerization temperature where the monomers polymerize around the fibers and form at least a portion of the composite article. The article may then be removed from the article template. Examples of the fiber-reinforced composite articles may include wind turbine blades for electric power generation.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of prior U.S. applicationSer. No. 12/724,024 filed Mar. 15, 2010, which is a continuation-in-partof U.S. application Ser. No. 12/008,041 filed Jan. 8, 2008. The entirecontents of the above-identified applications are herein incorporated byreference for all purposes.

BACKGROUND OF THE INVENTION

Fiber-reinforced composites are used in a variety of parts andequipment, including automotive parts, boat parts, building elements,and aircraft parts, among other types of articles. One well establishedmethod of making these articles is to place the bare fibers in a moldand then flow in the liquid precursors of a thermoset polymer. Once theprecursors have infused through the fibers and filled the mold, a curingstage ensues where the precursor polymerize into a thermoset polymermatrix surrounding the fibers. The fiber-reinforced composite may thenbe released from the mold and, if necessary, shaped, sanded, orotherwise processed into the final article.

Producing fiber-reinforced composites with widely available glass fibersand uncured thermoset resins is inexpensive and usually does not requirecomplex equipment or extreme processing conditions (e.g., hightemperatures) to produce the final articles. Still, there aresignificant disadvantages associated with making fiber-reinforcedthermoset articles, as well as deficiencies with the composites in manyapplications. One considerable disadvantage with making these articlesis the health and safety problems posed by working with uncuredthermoset resins. These resins often produce a lot of volatile organiccompounds (VOCs), many of which are irritants and even carcinogens.Outgasing VOCs are particularly problematic during curing processes whenexothermic polymerization reactions raise the temperature of thecomposite and increase rate which these compounds evaporate into thesurrounding atmosphere. In order to prevent VOC concentrations fromexceeding safe limits, expensive ventilation and air treatment equipmentis required. This equipment is particularly costly and difficult tomaintain for the manufacture of larger composite articles, such as boathulls and wind-turbine blades.

Another significant problem with making fiber-reinforced thermosetcomposites is the large amounts of unrecyclable waste they generate.Glass reinforced polyester and epoxy wastes do not easily decompose,making them expensive to landfill. When they are contaminated with toxicprecursors, such as epoxy prepregs, they present an even greaterenvironmental challenge. The inability to recycle most fiber-reinforcedthermosets also presents a disposal challenge when the articles madefrom these composites reach the end of their useful lives. The size ofthis challenge only increases with the size of the articles that must bediscarded.

Larger-sized articles present additional challenges for thermosetcomposites. Thermosets in general cannot be welded or melted, whichmakes it very difficult, if not impossible, to modify or repairthermoset parts once they have been cured. The high degree ofcrystallinity that is characteristic of many thermoset polymers alsomakes the composites prone to fractures that cannot easily be repaired.When fractures and other defects form in larger thermoset articles,often the only option is to replace the article at significant cost.

In view of the significant difficulties with both the manufacture andproperties of larger articles made from fiber-reinforced thermosetcomposites, alternative materials are being investigated. One areareceiving interest in replacing or blending the thermoset polymers withthermoplastic polymers. Thermoplastics have advantages over thermosetsin many article applications, including a usually superior fracturetoughness and chemical resistance that can increase the damage toleranceand useable lifetimes in larger articles. The increased toughness offiber-reinforced thermoplastic composites often means less material isneeded to make an article.

Starting monomers for many thermoplastics are less toxic than those ofwidely used thermosets, and they produce significantly less noxiousgases during article production. Many thermoplastics are also meltableand weldable, which allows larger parts to be repaired instead ofprematurely replaced. Thermoplastics are generally also recyclable,which significantly decreases environmental impact and waste disposalcosts both during manufacturing as well as at the end of an article'slifecycle.

Unfortunately, thermoplastics also have production challenges includingsignificantly higher flow viscosities than uncured thermoset resins. Theflow viscosities of widely used thermoplastic polymers may be orders ofmagnitude higher than uncured epoxy, polyester, and vinylester thermosetresins, which have flow viscosities comparable to water. The higher flowviscosities makes it difficult for thermoplastic resins to infiltrate afiber mat and produce a homogeneous polymer matrix composite that isfree of voids and seams. Oftentimes, it is necessary to introduce thethermoplastic resin under high temperature or high vacuum, whichincreases the costs and complexity of manufacturing processes. Thus,there is a need for new methods and materials to make fiber-reinforcedthermoplastic composites with reduced production problems and improvedbonding between the fibers and the polymer matrix. These and otherissues are address in the present application.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention include methods of making afiber-reinforced composite article. The methods may include providingfibers to an article template, where the fibers have been treated with acoupling-initiator compound. They may further include providing apre-polymerized mixture that includes a monomer and a catalyst to thearticle template. The combination of the fibers and the pre-polymerizedmixture may be heated to a polymerization temperature where the monomerspolymerize around the fibers and form at least a portion of thecomposite article. The article may then be removed from the articletemplate.

Embodiments of the invention further include additional methods ofmaking a fiber-reinforced composite article. The methods may includeproviding a pre-polymerized fiber-containing material comprising fibersin contact with a combination of a monomer and polymerization catalyst,where the fibers have been treated with a coupling-initiator compound.The method may also include applying the pre-polymerizedfiber-containing material to an article template, and heating thepre-polymerized fiber-containing material to a polymerizationtemperature. The monomers polymerize around the fibers to form at leasta portion of the composite article.

Embodiments of the invention still further include fiber-reinforcedcomposite articles. The articles may include a thermoplastic polymermatrix and fibers bonded to the thermoplastic polymer matrix by areacted coupling-initiator compound coupled to the fibers prior tocontact with thermoplastic polymer matrix. The coupling-initiatorcompound initiated the polymerization of the monomer to form thethermoplastic polymer. Examples of the fiber-reinforced compositearticles may include wind turbine blades for electric power generation.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the invention. The features and advantages ofthe invention may be realized and attained by means of theinstrumentalities, combinations, and methods described in thespecification.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the remaining portions of thespecification and the drawings wherein like reference numerals are usedthroughout the several drawings to refer to similar components. In someinstances, a sublabel is associated with a reference numeral and followsa hyphen to denote one of multiple similar components. When reference ismade to a reference numeral without specification to an existingsublabel, it is intended to refer to all such multiple similarcomponents.

FIG. 1 shows a flowchart with selected steps in methods of makingfiber-reinforced composite articles according to embodiments of theinvention;

FIG. 2 shows a flowchart with selected steps in additional methods ofmaking fiber-reinforced composite articles according to embodiments ofthe invention;

FIG. 3 illustrates a simplified cross-sectional drawing of an articletemplate for making a wind turbine blade according to embodiments of theinvention; and

FIG. 4 illustrates a simplified cross-sectional drawing of an articletemplate for a one-shot method of making a wind turbine blade accordingto embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Articles made from fiber-reinforced thermoplastic polymer composites aredescribed, as well as methods of making these articles. These articlesinclude, without limitation, equipment and parts for varioustransportation vehicles such as cars, trucks, boats, aircraft, trains,and non-motorized vehicles such as bicycles and sailboats, among otherkinds of transportation vehicles. The articles may further includeequipment and parts used in industrial applications, including parts forelectric power generation, such as wind turbine blades.

The present composite materials may be used to make large-sized articlesthat were previously made from a greater number of smaller pieces whichwere coupled together to make the larger article. The ability of thecomposites to make the article from a smaller number of pieces, or evena single piece, reduces manufacturing complexity as well as the numberof joints, fasteners, and seams that can weaken the overall structuralintegrity of the article. An exemplary longest dimension for a largearticle may be about 1 meter or more, about 5 meters or more, about 10meters or more, about 15 meters or more, about 20 meters or more, about25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100meters or more, among other ranges of a longest dimension.

The present methods permit the formation of fiber-reinforced compositearticles of larger sizes, increased fracture toughness and corrosionresistance, and longer operational lifetimes. These methods include theuse of fibers treated with one or more coupling-initiator compounds thatreact with and populate surfaces of the fibers that are subsequentlyexposed to the thermoplastic monomers which polymerize to form thepolymer matrix of the composite. The coupling end of thecoupling-initiator compounds are designed to react with and bond to thefiber, while the more distal oriented initiator can initiate a polymerchain from the surrounding monomers. By initiating polymerization soclose to the exposed surfaces of the fibers, and having a significantportion of the polymer directly bonded to the fibers through thecoupling-initiator compounds, the fibers are tightly coupled to thesurrounding polymer matrix in the composite. This tight coupling isbelieved to enhance several properties of the articles includingincreasing their fracture toughness and corrosion resistance.

The present methods also address the problem of high flow viscositiesthat complicate production processes with thermoplastic polymers.Instead of forming and melting the polymers before incorporating (e.g.,injecting) them into the an article mold, the polymers are formed insitu in the mold. This allows the lower viscosity monomers to beincorporated into the mold and infused around the fibers at lowertemperatures, in shorter times, and with fewer voids and other defectscaused by a slow flowing melted polymer.

The combinations of monomer and coupling-initiator compounds may beselected to have a controllable difference between the meltingtemperature of the monomer and its polymerization temperature. Forexample, the melting temperature of the monomer may be lower by about10° C. or more than its polymerization temperature. This permits themonomer to be melted and incorporated into an article mold for acontrolled period of time before increasing the monomer to itspolymerization temperature to perform in situ polymerization. It alsopermits variable control of the timing of the polymerization stageinstead of having to work with a fixed, predetermined time ofpolymerization. For example, inspections and quality checks may beperformed to insure the monomer is homogeneously distributed in the moldbefore the temperature is raised to the polymerization temperature. Incontrast, many conventional methods, in particular methods usingpre-polymerized thermoset resins, require fixed polymerization timesthat cannot be significantly accelerated or delayed.

In additional examples, solid monomer (e.g., particles, fiber prepreg,etc.) may be incorporated into the mold at temperatures below themonomer's melting point, before raising the temperature to between themelting and polymerization temperature. This allows the solid monomer tomelt and infuse around the fibers and conform to the shape of the moldbefore being polymerized. Examples may include combinations of addingsolid and liquid monomer to a mold at sequential stages prior topolymerization.

Exemplary Methods

FIG. 1 shows selected steps in an exemplary method 100 of making afiber-reinforced composite article according to embodiments of theinvention. The method 100 may include the step of providing fibers to anarticle template 102. The fibers are made from a material that can betreated with a coupling-initiator compound to bind the compound tosurfaces of the fibers that will be contacted by monomers that help formthe polymer matrix. Examples of fibers include glass fibers (e.g.,E-glass, etc.), ceramic fibers (e.g., aluminum oxide, silicon carbide,silicon nitride, silicon carbide, basalt, etc.), carbon fibers (e.g.,graphite, semi-crystalline carbon, carbon nanotubes, etc.), metal fibers(e.g., aluminum, steel, tungsten, etc.), and polymer fibers (e.g.,aramid, etc.). The fibers may be arranged as a mono-axial and/ormulti-axial, woven and/or non-woven mat. In addition, the fibers mayalso include chopped and/or unchopped (i.e., continuous fibers). Themats may have multiple sections with different weave styles, as well ascombinations of woven and non-woven sections. In addition, the mats mayhave regions where chopped fibers are incorporated, for example to allowbetter wet out and resin penetration in a preselected part or parts ofthe composite article.

The fibers are treated with one or more coupling-initiator compoundswhose coupling moieties can react with portions of the fibers to bindtogether the fibers and reacted compounds. In some contexts, acoupling-initiator compound may be referred to as a sizing compound thatenhances the binding between the fibers and surrounding polymer matrix.The coupling-initiator compound may also be referred to as an activatorcompound that starts the polymerization of the surrounding monomer isclose proximity to the fiber surface.

Specific coupling-initiator compounds may be selected based on the typeof fiber and thermoplastic used in the composite. Generally speaking,the coupling-initiator compounds may have the formula C—X—(I)_(n), whereC represents the coupling moiety, (I)_(n) represents n polymerizationinitiator moieties, and X represents a linking moiety that links the Cmoiety to the one or more I moieties. When the fibers are glass fibers,the coupling moiety C may include one or more silicon groups, and thecoupling-initiator compound may be represented by the formulaS—X—(I)_(n), where S represents a silicon-containing coupling moiety andX and (I)_(n) have the same meaning as described above.

The method 100 may further comprise providing a pre-polymerizedthermoplastic mixture to the article template 104. The pre-polymerizedmixture may include monomers and/or oligomers of the thermoplasticand/or a polymerization catalyst, among other components. Thepre-polymerized mixture may also include partially polymerized compoundssuch as dimers, trimers, and/or oligomers of the thermoplastic. Thepre-polymerized mixture may be added in the liquid phase to the articletemplate, or added in the solid phase. When the mixture is added in theliquid phase, it has a temperature at or above the melting point of thethermoplastic monomers and other components, but below a temperaturewhere significant polymerization of the monomers occur. When the mixtureis added in the solid phase, it may be added as particles to the articletemplate and/or exist as a pre-impregnated (“pre-preg”) coating on thefibers that are added to the template. Embodiments further includeproviding the pre-polymerized polymer mixture as both a liquid-phasemixture and solid-phase mixture to the article template.

In liquid-phase additions the monomer and the polymerization catalystmay be kept separate until they are provided to the article template.For example, the catalyst may be combined with the liquid-phase monomerimmediately before or during there introduction (e.g., injection) intothe article template. Alternatively, the monomer and catalyst may becombined and stored as a solid or liquid pre-polymerized mixture wellbefore their introduction to the article template. While the liquid andsolid phase mixtures of the pre-polymerized thermoplastic combined withcatalyst may exhibit some degree of polymerization—for example theformation dimers, trimers, and/or other oligomers—they are stillconsidered pre-polymerized mixtures since full polymerization initiatedby a coupling-initiator compound has not occurred. Similarly, pre-pregfibers that have a coating of B-stage thermoplastic materialssurrounding the fibers may still be considered a pre-polymerized mixtureor a component of the pre-polymerized mixture. For purposes of thisapplication, the discussions of polymerizations of the monomers may alsocover polymerizations of dimers, trimers, and/or other oligomers of thethermoplastic.

Examples of thermoplastic polymers whose monomers may be included in thepre-polymerized polymer mixture may include polybutylene terephthlalate(PBT), polyethylene terephthalate (PET), polyamide-6 (PA-6),polyamide-12 (PA-12), polyamide-6,6 (PA-6,6), cyclic poly(1,4-butyleneterephthalate) (CBT), polyurethanes (TPU), polymethylmethacrylate(PMMA), polycarbonates (PC), polyphenylenesulphide (PPS),polyethylenenapthalate (PEN), polybutylenenaphthalate (PBN), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK), and combinationsof two or more of these polymers, among other polymers.

One exemplary pre-polymerized polymer mixture includes lactam monomersthat produce polyamide (also called nylon) when polymerized. The lactammonomers may have the formula:

where R represents a C₃ to C₁₂ substituted or unsubstituted cyclichydrocarbon chain. The polymerization of these lactam monomers involvesthe opening of the cyclic hydrocarbon chain to make a linear chain withreactive carbonyl and amine groups separated by a —(CH₂)_(n)—hydrocarbon group.

One exemplary lactam monomer that enjoys wide commercial use iscaprolactam, which polymerizes into nylon 6. Other lactam monomers mayinclude butyrolactam (also known as 2-pyrrolidone) which polymerizesinto nylon 4; valerolactam which polymerizes into nylon 5; capryllactamwhich polymerizes into nylon 8; and lauryllactam which polymerizes intonylon 12; among other lacatams.

After the pre-polymerized mixture is provided to the article templateand made sufficient contact with the fibers, the combination of mixtureand fibers may be heated to a temperature where significantpolymerization of the monomers occur, as shown in step 106. In anexample where caprolactam is the monomer, the temperature of thepre-polymerized mixture may be raised from a melting temperature ofbetween about 80° C. and 120° C., to a polymerization temperature ofabout 120° C. or more (e.g., about 120° C. to about 220° C.). Inadditional examples, the pre-polymerized mixture may have a meltingtemperature of about 80° C. to about 200° C. (e.g., about 100° C. toabout 160° C.), and may have a polymerization temperature of about 120°C. to about 220° C. (e.g., about 180° C. to about 220° C.).

At the polymerization temperature, the polymerization-initiator moietiesfacilitate polymerization around the fibers. In the case of lactammonomers for example, the initiator moieties may have the formula:

where the carbonyl group is bonded to a linking moiety of thecoupling-initiator compound and R represents a C₃ to C₁₂ substituted orunsubstituted cyclic hydrocarbon chain. When the combination of thepre-polymer lactam mixture and fibers is raised to the polymerizationtemperature, the ring structure may open or be otherwise activated toinitiate a branched or unbranched polymerized chain from the initiatormoiety. The chain is coupled directly to the fiber through the couplingmoiety and linking moiety trunk of the coupling-initiator compound.

The polymerization of the lactam monomers may be facilitated by cationiccatalysts, anionic catalysts, and/or water. In cationic polymerizations,the catalyst may be an acid that protonates the carbonyl oxygen and/ornitrogen group on the lactam to start a nuclephilic reaction between theprotonated monomer and a second lactam monomer. This reaction may befollowed by a series of ring-opening acylations of the primary amine tobuild the polyamide chain.

In anionic polymerizations, the catalyst may include a base such as analkali metal, alkali-earth metal hydroxide, or alkali metal amide (amongother bases) that deprotonates the lactam nitrogen to form an anion thatreacts with a second lactam monomer. Subsequent proton transfer andpropagation reactions build the polyamide chain. In some instances, thereaction between the initial anion and the second lactam monomer may befurther facilitated by an activator compound, such as an acyl halide oranhydride (among other activators).

In hydrolytic polymerizations that involve water, polymerization may beinitiated when the water initiates a hydrolysis reaction that opens thelactam ring to form an amino acid. The amine group of the amino acidthen reacts with additional lactam monomers in subsequent ring-openingreactions to build the polyamide chain.

At least a portion of the polymer matrix formed by the polymerization ofthe lactam monomers is initiated by the initiator moieties on thecoupling-initiator compounds bound to the treated fibers. These moietiesstart the formation of straight and/or branched polyamide polymers whoformation is also aided by the one or more catalysts present. Thecoupling-initiator compounds create a covalently-bonded link between thesurface of the fibers and the surrounding polymers that is significantlystronger than a bond formed by simply curing a polyamide resin in thepresence of untreated fibers.

The present polymer matrices may also include polymers that are notdirectly bonded to the treated fibers. These polymers may have beenformed, for example, through polymerizations that were not initiated atan initiator moiety, and polymers that have fragmented or decoupledafter polymerization was initiated at the moiety. Although thesepolymers may not be directly bonded to the fibers, their columbic andphysical interactions with the directly bonded polymers may furtherstrengthen the bonding between the treated fibers and the surroundingpolymer matrix.

As the polymerization of the monomers around the fibers progress, afiber-reinforced composite is formed in the article template. Thecomposite material may form a portion or whole of the composite article108. The shape of the composite article may be defined, at least inpart, by the shape of the article template, which acts as a mold. Forexample, the article template may be shaped such that the compositeforms front or back half of a wind turbine blade that are joined insubsequent production steps. Alternatively, the article template may bedesigned for a one-shot fabrication of the composite article (e.g.,forming both halves of the blade from a single article template).

When the composite material has had sufficient time to solidify, it maybe removed from the article template 110. In some instances, removal maybe facilitated by applying release agents to the surfaces of the articletemplate that are exposed to the fibers and pre-polymerized mixturesthat form the composite article. These release agents hinder the fibersand polymerizing monomers from binding with the template as thecomposite is formed.

The composite material may be removed from the template either before orafter the polymer matrix has fully formed. In instances where thecomposite material is removed before curing is completed, the curing hasprogressed to the point where the article is sufficiently solid toretain the shape of the article after removal from the template. Theremoved article may undergo subsequent processing steps, such assanding, cutting, polishing, washing, drilling, coating, and/orpainting, among other post-formation steps. In the case where thecomposite is a portion of an article, the removed article may undergosteps to form the whole article, such as gluing, gap filling, and/orfastening the composite to other components to make the whole article.

Referring now to FIG. 2, a flowchart outlines selected steps inadditional methods of making fiber-reinforced composites according toembodiments of the invention. The methods 200 may include providing apre-polymerized fiber containing material (e.g., a pre-preg), where thefibers are in contact with a combination of the pre-polymerizedthermoplastic (e.g., monomers, oligomers) and a polymerization catalyst202. Examples of the pre-polymerized fiber may include glass fibers thathave been pre-treated with a coupling-initiator compound and coated witha pre-polymerized mixture of monomer and polymerization catalyst. Thepre-polymerized mixture may be applied above a melting temperature forthe monomers, but below a temperature where significant polymerizationof the monomers occur. Following the application of the monomers, thetreated fibers may be cooled to solidify the coating and stored untiluse.

That use may include applying the pre-polymerized fiber-containingmaterial to an article template 204 that may act as a mold for acomposite article. The pre-polymerized fiber-containing material may beapplied as a lay-up of fiber materials in the article template. In someembodiments the fibers may be arranged in a fiber mat before beingapplied to the template, or arranged to have a particular orientation orset of orientations during and/or after being layed-up in the template.

The methods 200 may optionally include applying additional layers offiber-containing material to the article template. These additionallayers may consist of untreated fibers, fibers treated withcoupling-initiator compounds that are not in contact with apre-polymerized mixtures, and additional layers of pre-polymerizedfiber-containing material. The fiber layers may be stacked on top ofeach other, and/or may be applied side-by-side in the article template.Embodiments may include positioning the pre-polymerized fiber-containingmaterial in specific locations of the article template to enhance thestrength and mass of the composite material in those areas. For example,one or more layers (or sections of layers) of the pre-polymerizedfiber-containing material may be positioned where the outer shell (i.e.,skin) of wind turbine blade makes contact with an internal supportstructure of the blade such as a rib and/or spar.

The methods 200 may also optionally include providing a pre-polymerizedmixture of monomers and polymerization catalyst to the article templatefollowing the lay-up of the fiber-containing materials. Thepre-polymerized mixture may be a combination of meltedmonomers/oligomers and catalyst provided to the fiber materials in thearticle template by, for example, resin transfer molding (RTM),vacuum-assisted resin transfer molding (VARTM), among other techniques.

After the pre-polymerized fiber-containing material (and any additionalmaterials) have been applied to the article template, the materials maybe heated to a temperature where the monomers polymerize to form acomposite material 206. The polymerization processes include theactivation of an initiator moiety on a coupling-initiator compound thathas been bound to the treated fiber. These moieties start the formationof polymers (e.g., polyamide polymers) that may be covalently linked tothe fibers, strengthening the bond between the fibers and thesurrounding polymer matrix. The composite material that results from thepolymerization processes may form either a portion or whole of afiber-reinforced composite article.

In some embodiments, the article template (or a portion thereof) maybecome part of the composite article. In these embodiments, thefiber-reinforced composite is bonded to one or more surfaces of thearticle template that were exposed to the pre-polymerizedfiber-containing material. The composite article that is formed includesan outer layer made from the article template. In additionalembodiments, the fiber-reinforced composite may optionally be removedfrom the article template 208, and the template may be discarded orprepared for forming another composite article.

Exemplary Methods of Making a Wind Turbine Blade

Exemplary methods of making a wind turbine blade will now be describedwith reference to the article templates shown in FIGS. 3 and 4respectively. FIG. 3 shows an article template 302 for part of the outerskin of a wind turbine blade made from a fiber reinforced composite. Thetemplate 302 may be for the side of the blade which faces the windduring operation of the turbine. A second article template (not shown)is used to form the opposite side of the blade. The two skins may thenbe joined using fasteners, adhesives, gap fillers, etc. to form theouter surface of the blade. Internal blade components, such as spars andribs, may also be added when the skins are joined together.

The article template 302 may be made from a rigid material that has aninner surface 306 defining the shape of the outer skin. This surface maybe made from a material or treated (e.g., coated) to form a exposedlayer of material that facilitates the release of the fiber-reinforcedcomposite outer skin from the article template 302.

The article template 302 may further comprise a vacuum bag 308 that maybe fluid-tightly sealed to the peripheral edges of the template.Together, the liner of the vacuum bag 308 and inner surface 306 definean enclosed volume where the materials for the composite may be combinedand heated to form the fiber-reinforced composite outer skin.

The article template 302 may further include openings 310 and 312,through which pre-polymerized liquid mixtures of monomer and catalystmay flow to make contact with the fiber materials shown in fiber layer314. As noted above, additional pre-polymerized materials (e.g., solidpre-preg materials) may also be present with the fibers in the fiberlayer 314.

When the vacuum bag 308 is evacuated, the change in air pressure betweenthe inside and outside of the vacuum bag 308 may press the bag lineragainst the fiber layer 314. In addition, a pressure differential causesthe pre-polymerized mixture to flow through openings 310 and 312 toinfiltrate the fiber layer 314. In the embodiment shown, the flowingmixture may form two fluid fronts at the forward and read ends of theouter skin which may converge proximate to the middle of the skin.Additional flow configurations are possible depending upon the numberand positioning of the openings in the article template.

When the pre-polymerized mixture has been distributed over the fiberlayer 314, the materials may be heated to a polymerization temperatureto start the formation of the fiber-reinforced composite. The heatingmay, for example, be carried out by a heating element 316 positionedproximate to the inner surface 306 of the article template 302. When thepolymerization process is sufficiently advanced, the nascent compositemay be allowed to cool at a pre-defined rate to ensure the outer skin isformed with the requisite mechanical properties. The outer skin may thenbe removed from the article template 302 so that it can be combined withthe other parts of the blade. The article template may be treated (e.g.,cleaned and prepared) to form another outer skin.

The article template 302 shown in FIG. 3 forms only a part of the outerskin of a wind turbine blade. FIG. 4 shows an article template 402 thatis designed to form a more complete outer skin for a wind turbine bladewith a one-shot manufacturing technique. The article template 402includes a first mold component 404 and a second mold component 406which are combined to form the one-shot article template 402. The firstand second mold components may have peripheral edges 408, 410 that canbe joined to form an air-tight seal.

One-shot methods of making a wind turbine blade with article template402 may include laying-up fiber materials in the first mold component404 to form a first fiber layer 412 in the component. Additionalmaterials such as particles of pre-polymerized monomer and catalyst, mayalso be added to the mold component 404 and/or fiber layer 412. Firstand second internal support sections 414, 416 may be placed in the firstmold component 404 over the first fiber layer 412. The first and secondinternal support sections 414, 416 may be made from rigid materials suchas wood, ceramic, light-weight metal or alloy, and/or polymers, amongother materials. The rigid material may be surrounded by a more flexiblematerial (e.g., foam rubber) and a flexible membrane that may makecontact with the fiber layers in the template 402.

An additional fiber layer 418 may support a gap between the first andsecond support sections 414, 416. This fiber layer 418 may be convertedinto an internal support of the final composite that joins oppositesides of the blade for increased strength and stability. In additionalembodiments, two or more internal supports (or conversely no supports)may be formed in blade.

Another additional fiber layer 420 may be layed-up over the first andsecond support structures 414, 416 such that the ends of the fiber layer420 overlap or otherwise contact the complementary ends of first fiberlayer 412. The second mold component 406 may then be placed over thefiber layers and internal supports and secured to first mold component404 along the peripheral edges 408, 410.

Openings (not shown) in the article template 402 may be coupled tovacuum lines that create vacuum channels in the enclosed spaces betweenthe mold components 404, 406, and outer surfaces of support sections414, 416. When the channels are evacuated, positive pressure exertedfrom inside the support sections 414, 416 may push their outer flexiblemembranes into the surrounding fiber layers 412, 420 to press themagainst inside surfaces of the article template 402. The evacuation ofthe channels also creates a pressure gradient for the flow of apre-polymerized mixture through the fiber layers.

Following the addition of the pre-polymerized materials with the fiberlayers, the combination may be heat cured to polymerize the monomers andform the fiber reinforced composite article. The heating may be done bya heat transfer system 422, 424, such as heating filaments integratedinto the first and second mold components 404, 406.

Once the composite article has sufficiently cured, the mold components404, 406 may be separated and the fiber-reinforced composite windturbine blade removed from the article template 402.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Accordingly, the above description should not betaken as limiting the scope of the invention.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the fiber” includesreference to one or more fibers and equivalents thereof known to thoseskilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

What is claimed is:
 1. A method of making a fiber-reinforced compositearticle, the method comprising: providing a pre-polymerizedfiber-containing material comprising fibers in contact with acombination of a monomer and polymerization catalyst, wherein the fibershave been treated with a coupling-initiator compound and thecoupling-initiator compound has the formula:S—X—(I)_(n) wherein n is an integer having a value between 1 and 5, Scomprises a silicon-containing coupling moiety through which thecoupling-initiator compound bonds to a substrate surface on the fibers,X comprises a linking moiety to link the S moiety with the one or more Imoieties, and (I)_(n) comprises one or more polymerization initiatormoieties, wherein each of the initiators moieties is capable ofinitiating a polymerization of the monomer at the polymerizationtemperature, and wherein each of the initiator moieties is the same ordifferent; applying the pre-polymerized fiber-containing material to anarticle template; subsequently adding more of the monomer to the articletemplate; and heating the pre-polymerized fiber-containing material to apolymerization temperature where the monomers polymerize around thefibers to form at least a portion of the composite article, wherein thefiber-reinforced composite is bonded to one or more surfaces of thearticle template such that the composite article formed includes anouter layer comprising at least a portion of the article template withinthe layer structure.
 2. The method of claim 1, wherein thepolymerization temperature is about 120° C. to about 220° C.
 3. Themethod of claim 1, wherein the combination of the monomer andpolymerization catalyst is a solid at room temperature, and thepre-polymerized fiber-containing material is solid when applied to thearticle template.
 4. The method of claim 3, wherein the methodcomprises: heating the solid pre-polymerized fiber-containing materialto a melting temperature where the monomer melts but does notpolymerize; and infusing the molten monomer around the fibers beforeraising the pre-polymerized fiber-containing material to thepolymerization temperature.
 5. The method of claim 3, wherein themelting temperature may have a range from about 80° C. to about 120° C.6. The method of claim1, wherein the monomer comprises a lactam and thepolymerized monomers comprise a polyamide.
 7. The method of claim 6,wherein the lactam monomer comprises capropactam and the polyamidecomprises nylon
 6. 8. The method of claim 1, wherein the fibers compriseglass fibers arranged as a mono-axial or multi-axial, chopped fiber orunchopped fiber, woven or non-woven mat.